Microstructure and Properties of Hybrid Laser Arc Welded Joints (Laser Beam-MAG) in Thermo-Mechanical Control Processed S700MC Steel

Abstract

The article presents the microstructure and properties of joints welded using the Hybrid Laser Arc Welding (HLAW) method laser beam-Metal Active Gas (MAG). The joints were made of 10-mm-thick steel S700MC subjected to the Thermo-Mechanical Control Process (TMCP) and characterised by a high yield point. In addition, the welding process involved the use of solid wire GMn4Ni1.5CrMo having a diameter of 1.2 mm. Non-destructive tests involving the joints made it possible to classify the joints as representing quality level B in accordance with the ISO 12932 standard. Destructive tests of the joints revealed that the joints were characterised by tensile strength similar to that of the base material. The hybrid welding (laser beam-MAG) of steel S700MC enabled the obtainment of good plastic properties of welded joints. In each area of the welded joints, the toughness values satisfied the criteria related to the minimum allowed toughness value. Tests involving the use of a transmission electron microscope and performed in the weld area revealed the decay of the precipitation hardening effect (i.e., the lack of precipitates having a size of several nm) and the presence of coagulated titanium-niobium precipitates having a size of 100 nm, restricting the growth of recrystallised austenite grains, as well as of spherical stable TiO precipitates (200 nm) responsible for the nucleation of ferrite inside austenite grains (significantly improving the plastic properties of joints). The tests demonstrated that it is possible to make welded joints satisfying quality-related requirements referred to in ISO 15614-14.

Effect of the t8/5 Cooling Time on the Properties of S960MC Steel in the HAZ of Welded Joints Evaluated by Thermal Physical Simulation

“…Combining multiple techniques into one-the use of so-called hybrid technologies-is also one of the ways to achieve HSLA welded joints with satisfactory properties. Górka [14] examined hybrid welding technologies (laser beam + MAG) of S700MC steel T-joints with a thickness of 10 mm. Sajek and Nowacki [15] applied the same technology to S960QL.…”

Laser Hybrid Butt Welding of Large Thickness Naval Steel

“…LAHW presented a greater development in the nineties due to the availability of CO2 lasers that could concentrate densities of higher powers, up to 10 6 W/cm 2 . Since then, several studies have been focused on materials approach applied on steel [10,13], titanium [14,15], aluminium alloys [16,17] or dissimilar joints [18,19]. Diverse investigations have been carried out to face different aspect of the process, as the economic viability of the laser-arc hybrid welding process, the influence of the relative position of the laser beam and the torch of the electric arc, edge preparation, minimization of metallurgical defects, optimization of process parameters, etc [20][21][22][23].…”

“…The results of his research clearly showed the advantages of combining a laser beam and an electric arc for welding. The hybridization effect of the plasma arc with a CO 2 laser beam showed a remarkable increase in the welding speed (up to 100%), the weld depth (penetration) and the stability of the process [10]. After the demonstrated success of the application of this technique, the research and development of LAHW underwent a slow growth, due to the lack of availability of high power lasers.…”

Laser Welding

“…The present special issue on "Laser Welding" was a success with a total of 16 original research works published after peer-review. Different topics were discussed within this special issue: modelling and simulation of laser welding were presented in [1][2][3][4]; porosity control by means of high speed imaging and microscopy techniques was studied and discussed [5]; the effect of processing parameters on the microstructure and mechanical properties of laser-welded joints was evaluated for different metallic systems such as AZ31 alloy [6], steels [7][8][9][10], Ti-based alloys [11][12][13], and Al-based alloys [14]; and finally, dissimilar laser welding of aluminum to steel was presented [15,16].…”